1. Field of the Invention
This invention relates to coating articles with a liquid and more particularly to a system for spraying a liquid wax coating onto a moving stream of fruit, vegetables or the like.
2. Description of the Prior Art
Prior fruit coating systems spray a liquid wax coating onto a layer or stream of fruit as the fruit is conveyed beneath a single spray nozzle. The nozzle is moved transversely back and forth across the moving stream of fruit and sprays continuously during its back and forth motion. The resultant spray pattern provides doubly sprayed zones alternating with lightly sprayed zones along both sides of the moving surface. In order to provide a uniform density, large area spray pattern air under pressure is directed into and mixed with the liquid stream emerging from the nozzle.
When spraying volatile liquids, such as the liquid wax coating for fruit employed in the preferred embodiment of the invention, the mixing of a stream of pressurized air with the liquid (as required by a single large nozzle) may have undesired effects. For example, when using a "pneumatic" spray, the liquid may dry before the impact with the surface. This renders the coating on the fruit translucent and visible (fogging) instead of transparent. Furthermore, the mixing of air at the nozzle requires additional piping to the nozzle and careful nozzle adjustment. It also requires the use of a vapor collecting hood to protect operating personnel. Furthermore, mechanical systems for rapidly traversing the nozzle requires frequent replacement of worn parts during prolong continuous service.
The patent to Gerwe et al U.S. Pat. No. 2,866,709, Dec. 30, 1958, assigned to the assignee of the present invention, discloses a method of treating peaches wherein the fruit is supported on a brush bed and is sprayed by a row of fixed nozzles controlled by a common valve. No sequential nozzle operation is disclosed. When all the nozzles in a row of nozzles were turned on to spray simultaneously, the flow of wax to the nozzle manifold would require adjustment in accordance with the number of nozzles in a row.